Perhaps the most striking difference between fungal cells and human cells is that fungal cells are encased in a wall that protects them from an osmotically and immunologically hostile external environment. In addition, the fungal cell wall relays signals for invasion and infection of a likely plant, animal, or human host. The cell wall is not an inert outer layer, but rather plays a dynamic role in all aspects of fungal physiology, e.g., morphogenesis, metabolite transport, protein secretion, intracellular signaling, and cell-cell contact. Cell-wall structure is now well characterized, at least in the ascomycetes, and appears to be very similar in human pathogens including Candida albicans, Penicillium spp., and Aspergillus spp. The fact that human cells lack a cell wall and the underlying biosynthetic and regulatory machinery to make the wall, suggests that drugs targeting cell-wall synthesis and assembly will be safe and specific antifungals. Current treatments for fungal infections are limited by few therapeutic options; these include amphotericin B, which interacts with membrane sterols, and a variety of azoles and allylamines that inhibit membrane sterol biosynthesis. Unfortunately, amphotericin B is toxic to humans and clinical resistance to azoles is increasing. These observations underscore the clear need for new antifungals. In this Phase I SBIR application, we propose to develop a novel screen that identifies inhibitors of transcription of a key gene for fungal cell-wall assembly, namely, the catalytic subunit of (1,3) beta-glucan synthase activity. This will be accomplished in two specific aims: Aim One: Development of a screen to identify inhibitors of transcription of the FKS gene encoding the catalytic subunit of (1,3) beta -glucan synthase. Aim Two: Screen 3,000 pure compounds for inhibitors of transcription of the (1,3) beta -glucan synthase FKS gene. Importantly, we will determine the effect of putative inhibitors on fungal growth, on human-cell toxicity, and on the levels of FKS message. This work will lead to a novel assay that will be used for the discovery of new antifungal compounds. In turn, these novel compounds will be developed for the treatment of human fungal diseases.